Solventless hot melt process for the preparation of pressure sensitive adhesives

The incorporation of a non-thermosettable phenolic tackifying resin surprisingly provides improved solvent free, hot melt processing of hydrocarbon elastomers with crosslinking promoters to form pressure sensitive adhesive tapes. The tapes advantageously have a desirable balance of the properties of resistance to slow rate peel and fast rate peel adhesion.

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Claims

1. A solventless hot melt process for preparing a pressure sensitive adhesive from a tackified hydrocarbon elastomer, said process occurring in a continuous compounding device which has a sequence of alternating conveying and processing zones, said processing zones being capable of masticating and mixing, said process comprising the steps of:

(a) feeding a hydrocarbon elastomer to a first conveying zone to transport said elastomer to a first processing zone;
(b) masticating said elastomer in the first processing zone for a time sufficient to render it capable of (i) receiving adjuvants, and (ii) being extruded as a solventless hot melt pressure sensitive adhesive;
(c) transporting said masticated elastomer from the first processing zone to subsequent processing and conveying zones wherein a crosslinking promoter and a non-thermosettable phenolic tackifying resin are added and mixed therewith to form a blend said crosslinking promoter reacts with radicals to produce crosslinks; and
(d) discharging said blend from said continuous compounding device, wherein said blend comprises a solventless hot melt pressure sensitive adhesive.

2. A process according to claim 1 wherein step (c) comprises the step of adding said crosslinking promoter and said non-thermosettable phenolic tackifying resin together as a blend.

3. A process according to claim 1 wherein step (c) further comprises the step of adding a non-phenolic tackifying resin.

4. A process according to claim 3 wherein step (c) comprises the addition of a blend of crosslinking promoter and non-thermosettable phenolic tackifying resin after said non-phenolic tackifying resin is added and blended with said masticated elastomer.

5. A process according to claim 3 wherein said step (c) comprises the addition of said non-phenolic tackifying resin at a rate sufficient to provide 1 to 400 parts by weight non-phenolic tackifying resin per 100 parts by weight elastomer.

6. A process according to claim 1 wherein said blend is discharged from said continuous compounding device as a thin film onto a moving web and exposed to radiation.

7. A process according to claim 6 wherein said radiation is selected from the group consisting of electron beam radiation and ultraviolet light.

8. A process according to claim 1 comprising the further step of adding adjuvants to said elastomer.

9. A process according to claim 1 wherein said elastomer comprises at least 50 percent by weight natural rubber.

10. A process according to claim 1 wherein said non-thermosettable phenolic tackifying resin is selected from the group consisting of phenol-aldehyde condensates, terpene-phenol reaction products, and phenolic reaction products.

11. A process according to claim 1 wherein said crosslinking promoter is selected from the group consisting of aromatic, aliphatic and heteroatomic monomers and oligomers containing at least two carbon--carbon double bonds.

12. A process according to claim 1 wherein said crosslinking promoter comprises moieties selected fro the group consisting acrylate, allylic and maleimide moieties.

13. A process according to claim 1 wherein said step (c) comprises the addition of said crosslinking promoter at a rate sufficient to provide 0.10 to 10 parts by weight crosslinking promoter per 100 parts by weight elastomer.

14. A process according to claim 1 wherein said step (c) comprises the addition of said non-thermosettable phenolic tackifying resin at a rate sufficient to provide 0.10 to 15 parts by weight non-thermosettable phenolic tackifying resin per 100 parts by weight elastomer.

15. A process according to claim 1 wherein said blend is discharged onto a moving web to form a thin film thereon.

Referenced Cited
U.S. Patent Documents
4588637 May 13, 1986 Chiu
4678794 July 7, 1987 Huddleston et al.
5242727 September 7, 1993 Briddell et al.
Foreign Patent Documents
6128542 May 1994 JPX
7126590 May 1995 JPX
WO 94/11175 May 1994 WOX
Other references
  • Rubbercon '77, "Delayed Action Peroxide Vulcanization Systems", Y.W. Chow and G.T. Knight, pp. 24.1-24.12. (No date avail.). Rubbercon '77, "New Developments in Rubber-Bound Antioxidants", Gerald Scott, pp. 19/1-19/18. (No date avail.). Rubber World, "Crosslinking plasticizers for injection molding", J. Edgar Lohr, Jr., et al., pp. 47-51, Oct. 1971. Schenectady Chemicals Inc., Material Data Sheets for SP-1068, SP-1077, SP-553, SP-560, SP-6701, and CRJ-418 Resins. (No data avail.).
Patent History
Patent number: 5914157
Type: Grant
Filed: Aug 31, 1995
Date of Patent: Jun 22, 1999
Assignee: Minnesota Mining and Manufacturing Company (St. Paul, MN)
Inventors: Daniel C. Munson (St. Paul, MN), Andrew C. Lottes (St. Paul, MN), Angelo Psellas (Brockville), Denis A. Brisson (Brockville)
Primary Examiner: Bernard Pianalto
Attorney: Doreen S. L. Gwin
Application Number: 8/521,921